Intraplaque release of inflammatory cytokines from macrophages is implicated in atherogenesis by inducing the proliferation and migration of media smooth muscle cells (SMCs). PCSK9 is present and released by SMCs within the atherosclerotic plaque but its function is still unknown. In the present study, we tested the hypothesis that PCSK9 could elicit a pro-inflammatory effect on macrophages. THP-1-derived macrophages and human primary macrophages were exposed to different concentrations (0.250 ÷ 2.5 µg/ml) of human recombinant PCSK9 (hPCSK9). After 24 h incubation with 2.5 µg/ml PCSK9, a significant induction of IL-1β, IL-6, TNF-α, CXCL2, and MCP1 mRNA, were observed in both cell types. Co-culture of THP-1 macrophages with HepG2 overexpressing hPCSK9 also showed the induction of TNF-α (2.4 ± 0.5 fold) and IL-1β (8.6 ± 1.8 fold) mRNA in macrophages. The effect of hPCSK9 on TNF-α mRNA in murine LDLR^−/− bone marrow macrophages (BMM) was significantly impaired as compared to wild-type BMM (4.3 ± 1.6 fold vs 31.1 ± 6.1 fold for LDLR^−/− and LDLR^+/+, respectively). Finally, a positive correlation between PCSK9 and TNF-α plasma levels of healthy adult subjects (males 533, females 537) was observed (B = 8.73, 95%CI 7.54 ÷ 9.93, p < 0.001). Taken together, the present study provides evidence of a pro-inflammatory action of PCSK9 on macrophages, mainly dependent by the LDLR.

Genetic, epidemiological and pharmacological data have led to the conclusion that antagonizing or inhibiting Proprotein convertase subtilisin/kexin type 9 (PCSK9) reduces cardiovascular events. This clinical outcome is mainly related to the pivotal role of PCSK9 in controlling low-density lipoprotein (LDL) cholesterol levels. The absence of oral and affordable anti-PCSK9 medications has limited the beneficial effects of this new therapeutic option. A possible breakthrough in this field may come from the discovery of new naturally occurring PCSK9 inhibitors as a starting point for the development of oral, small molecules, to be used in combination with statins in order to increase the percentage of patients reaching their LDL-cholesterol target levels. In the present review, we have summarized the current knowledge on natural compounds or extracts that have shown an inhibitory effect on PCSK9, either in experimental or clinical settings. When available, the pharmacodynamic and pharmacokinetic profiles of the listed compounds are described.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is one of the key regulators of low-density lipoprotein cholesterol plasma levels. Circulating PCSK9, which differs between genders, represents a valid pharmacological target for preventing cardiovascular (CV) events. We aimed to investigate sex-related associations between PCSK9 plasma levels and biochemical and anthropomorphic factors, and familial and personal morbidities, in a large European cohort (n = 3673) of men (47.9%) and women (52.1%). Individuals (aged 54-79 years) free of CV diseases were enrolled in seven centers of five European countries: Finland, France, Italy, the Netherlands, and Sweden. PCSK9 plasma levels were measured by ELISA. PCSK9 was higher in women than in men. Multiple linear regression analysis showed that latitude, sex, and treatments with statins and fibrates were the strongest predictors of PCSK9 in the whole group. These variables, together with triglycerides and high-density lipoprotein cholesterol, were also associated with PCSK9 in men or women. Mean corpuscular hemoglobin concentration and pack-years were PCSK9 independent predictors in women, whereas hypercholesterolemia and physical activity were independent predictors in men. The associations between PCSK9 and latitude, uric acid, diabetes, hypercholesterolemia and physical activity were significantly different in men and women (p_interaction <0.05 for all). Besides confirming the association with lipids in the whole group, our study revealed previously unknown differences in PCSK9 predictors in men and women. These might be taken into account when defining individual risk for CV events and/or for refining PCSK9 lowering treatments.

The new complexes [RuCl₂(η⁶-p-cymene)(κP-Ph₂PR)] [R = 4-C₆H₄OSiMe₂ ^tBu, 1; R = 4-C₆H₄Br, 2; R = OC(O)CHCl₂, 3; R = OPh, 4; R = O(2-C₆H₄SiMe₂ ^tBu), 5] and [Ru(C₂O₄)(η⁶-p-cymene){κP-Ph₂PO(2-C₆H₄(SiMe₂ ^tBu))}], 6, were obtained in 83–98% yield from Ru(II) arene precursors by three different synthetic strategies. The unprecedented phosphine Ph₂P(O(2-C₆H₄SiMe₂ ^tBu)) was synthesized in 86% yield from 2-C₆H₄Br(OSiMe₂ ^tBu) and Ph₂PCl, via intramolecular oxygen to carbon 1,3 migration of the silyl group (retro-Brook rearrangement). All the complexes were fully characterized by analytical and spectroscopic methods, and by single crystal X-ray diffraction in the cases of 3, 4, 5 and 6. Complexes 1–6 and the model compounds [RuCl₂(η⁶-p-cymene)(κP-PPh₃)] (Ru-PPh₃) and [Ru(C₂O₄)(η⁶-p-cymene)(κP-PPh₃)] (Ru-PPh₃-O) underwent slow degradation in chloroform solutions upon air contact; the mixed valence complex [(η⁶-p-cymene)Ru(μ-Cl)₃RuCl₂(κP-PPh₃)], 7, was isolated from a solution of Ru-PPh₃ in CHCl₃, and X-ray identified. The antiproliferative activity of 1–6 and Ru-PPh₃, Ru-PPh₃-O and [RuCl₂(η⁶-p-cymene)(κP-PTA)] (RAPTA-C) was assessed towards the triple-negative breast cancer cell line MDA-MB-231, the ovarian carcinoma cell line A2780 and human skin fibroblasts (HSF). Complexes 1, 2, 5 and 6 displayed IC₅₀ values significantly lower than that of cisplatin, with 2 providing a more potent cytotoxic effect on MDA-MB-231 and A2780 cancer cells compared to the noncancerous cell line (HSF). The stability of all complexes in DMSO/water solution was elucidated by NMR and conductivity measurements, and in particular ³⁵Cl NMR spectroscopy was helpful to check the possible chloride dissociation. The stability studies suggest that the cytotoxic activity in vitro of the compounds is mainly ascribable to Ru(II) species still bound to the phosphorus ligand.

Genetic and clinical studies have demonstrated that loss-of-function variants in the angiopoietin-like 3 (ANGPTL3) gene are associated with decreased plasma levels of triglycerides (TGs), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), which leads to a significant reduction in cardiovascular risk. For this reason, ANGPTL3 is considered an important new pharmacological target for the treatment of cardiovascular diseases (CVDs) together with more conventional lipid lowering therapies, such as statins and anti proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies. Experimental evidence demonstrates that anti-ANGPTL3 therapies have an important anti-atherosclerotic effect. Results from phase I clinical trials with a monoclonal anti-ANGPTL3 antibody (evinacumab) and anti-sense oligonucleotide (ASO) clearly show a significant lipid lowering effect. In addition, from the analysis of the protein structure of ANGPTL3, it has been hypothesized that, beyond its inhibitory activity on lipoprotein and endothelial lipases, this molecule may have a pro-inflammatory, pro-angiogenic effect and a negative effect on cholesterol efflux, implying additional pro-atherosclerotic properties. In the future, data from phase II clinical trials and additional experimental evidence will help to define the efficacy and the additional anti-atherosclerotic properties of anti-ANGPTL3 therapies beyond the already available lipid lowering therapies.